The technique for soldering an electronic component to a busbar disclosed in JP 2004-147416A, for example, is known as a conventional technique for soldering an electronic component to a busbar. JP 2004-147416A discloses a technique for providing a punched portion of a busbar constituted by a slit or a small hole that is to be located on the outside of and along the outer edge of a connection terminal provided on the back side of an electronic component such as a semiconductor switching element in order to restrict the spread of solder and position the electronic component on a proper installing surface with high accuracy when the electronic component is soldered to the busbar. At that time, the punched portion blocks the spread of paste-like solder applied to the terminal installing surface of the busbar. The solder is thus bulged due to surface tension, and the bulged solder is pressed onto the outer surface of the terminal. As a result, the electronic component is installed on the busbar without being shifted from the proper installing position.
However, with the above-mentioned conventional technique, the electronic component can be installed on the busbar without being shifted from the proper installing position, whereas a space in which the punched portion constituted by a slit or a small hole is to be provided is required on the busbar. Therefore, this is disadvantageous for a further reduction in size of a circuit assembly. Moreover, the surface tension of solder is utilized, and therefore, it is not easy to restrict the spread of solder with high accuracy.
The technique disclosed in this specification was accomplished based on the above-mentioned circumstances, and, according to this specification, a circuit assembly with which the spread of solder can be restricted with high accuracy when an electronic component is soldered to a busbar is provided, while the size of the circuit assembly can be further reduced.